For those recommending Deadwood, have you even seen seasons 2 and 3? I mean, yeah, season 1 is fucking awesome but season 2 and 3 (especially season 3!) are a complete trainwreck. The Shakespearean dialogue goes into hyperdrive and by the end of the series nothing has happened. I've never seen a more anticlimactic end to anything in my entire life. The last episode in season 3 is like one gigantic "fuck you!" to the viewer.
The only way I could ever recommend Deadwood to anyone is if they stop at the end of season 1 and just forget that there's a season 2 and 3 out there.